# The Fate of Dense Scalar Stars

## TL;DR

This paper investigates the long-term behavior of scalar stars, such as axion stars, using full general relativity simulations, revealing conditions under which they are stable or collapse into black holes, with implications for cosmology and gravitational waves.

## Contribution

It provides the first comprehensive numerical analysis of scalar star fate including gravity, showing how different potentials influence stability and collapse, and discusses cosmological consequences.

## Key findings

- KKLT potentials lead to meta-stable scalar stars.
- Alpha-attractor potentials can cause collapse to black holes.
- Different potentials imply varied gravitational wave signatures.

## Abstract

Long-lived pseudo-solitonic objects, known as oscillons/oscillatons, which we collectively call real scalar stars, are ubiquitous in early Universe cosmology of scalar field theories. Typical examples are axions stars and moduli stars. Using numerical simulations in full general relativity to include the effects of gravity, we study the fate of real scalar stars and find that depending on the scalar potential they are either meta-stable or collapse to black holes. In particular we find that for KKLT potentials the configurations are meta-stable despite the asymmetry of the potential, consistently with the results from lattice simulations that do not include gravitational effects. For $\alpha$-attractor potentials collapse to black holes is possible in a region of the parameter space where scalar stars would instead seem to be meta-stable or even disperse without including gravity. Each case gives rise to different cosmological implications which may affect the stochastic spectrum of gravitational waves.